1. Field of the Invention
The present invention relates to an electronic device having a bezel structure to fix constituent elements, and more particularly, to an electronic device having a bezel structure which can restrict radiation of an electromagnetic field from a loop formed by the bezel.
2. Description of the Related Art
In general, electronic devices, such as screen incorporated projectors or LCD monitors, use a metal bezel to firmly support constituent elements, such as a screen. The bezel has a loop shape because a central portion of one of the constituent elements must not be blocked by the bezel.
FIG. 1 is a perspective view illustrating a general projection television as an example of an electronic device. Referring to FIG. 1, the projection television includes a case 1, a screen 3 installed to the case 1, a loop shaped bezel 5 to fix the screen 3 to the case 1, and an electronic unit 7 provided in the case 1. The case 1 and the screen 3 are formed of an insulation material such as plastic while the bezel 5 is formed of a conductive material, such as aluminum. The electronic unit 7 includes an optical projection unit, such as an optical system for projection, and an electronic circuit to drive the optical projection unit.
In the electronic device having the above structure, the electronic unit 7 including the electronic circuit is arranged close to the bezel 5 as a size of the electronic device decreases. When the electronic unit 7 is arranged close to the bezel 5, as shown in FIG. 2, a near field 9 generated by the electronic unit 7 is electronically coupled to the bezel 5 having a loop shape. Thus, the bezel 5 forms a loop antenna at and around a resonance frequency.
Assuming that a total length of a loop formed by the bezel 5 is L1, the following Equation 1 is satisfied.L1=k×λ0  [Equation 1]
Here, the total length of the loop “L1” is twice a sum of a width W and a height H of the bezel 5. That is, L1=2×(H+W). “k” denotes an expansion rate of a wavelength and is not less than 1.0 in a free space. The expansion rate “k” changes according to a size of the bezel 5 and the electronic circuit 7 arranged around the bezel 5. “λ0” denotes a resonance wavelength.
When the bezel 5 having the above structure is employed, the bezel 5 resonates at the resonance wavelength “λ0” and a minimum resonance frequency f is about 300/λ0 MHz. Accordingly, the near field 9 generated by the electronic unit 7 at and around the resonance frequency increases so that the increased near field 9 causes problems in that electronic field radiation and electro-magnetic interference (EMI) increase.
In order to solve the above problems, a conventional electronic device has been suggested to shield the electronic circuit or the electronic unit and to form the bezel supporting the screen with an insulation material. Also, in order to solve a problem in the strength of the bezel 5, an additional metal plate to reinforce the bezel 5 is provided in the conventional electronic device. The above solutions, however, have drawbacks, such as an increase in weight, deterioration in assembly, lowering in mechanical strength, and an increase in manufacturing cost.